which energy bar?

Some meal-replacement bars may not have as much protein as you think. You won't find pig's feet or cattle hide listed in the fine print, but that's because they're hidden behind names like gelatin, hydrolyzed collagen, or hydrolyzed gelatin. Both collagen and gelatin lack an essential amino acid required to make them a complete protein. That means the quality of the protein is inferior to products that lack gelatin or collagen.

Look for a bar that lists whey or casein protein—or a blend of both—as the first or second ingredient. These milk proteins contain all the essential amino acids your muscles need. Baylor University researchers found that when men with at least 6 weeks of weight training experience were given a whey-casein mixture before their workouts, they built 50 percent more lean muscle mass over 10 weeks than men who took only whey.

“All-natural protein” is often code for soy, which research shows may cause gynocomastia—the abnormal enlargement of the mammary glands in men. When you consume soy protein, you’re actually courting the Mr. Hyde side of two organic compounds: genistein and daidzein. Both act so similarly to estrogen that they’re known as phytoestrogens (plant produced estrogen). Eat enough of the stuff, and you open up the potential for hormonal havoc.

Many allegedly healthy bars contain high fructose corn syrup, which quickly raises blood sugar and cancels out any of the potential benefits you might otherwise get from healthy ingredients like oats. Take Health Valley Low Fat Chocolate Chip Granola Bars, for example. The main ingredient is brown rice syrup—a euphemism for sugar. You’re better off snacking on good old-fashioned cheese and crackers to swap out sugar and calories for protein and fiber.

If you’re tied to the convenience of a bar, look for labels with no more than five ingredients. “The longer the list and the more unpronounceable the words are, the farther it is from real food,” says Jonny Bowden, Ph.D, CNS Board Certified Nutrition Specialist.

Unless you’re recovering from a grueling workout or running a marathon, opt for nutrient-packed snacks

Reduced-sugar and sugar-free bars appeal to carb-conscious consumers because they have little impact on blood sugar—but not without a price. Sugar alcohols like malitol and sorbitol can cause uncomfortable side effects such as gas, bloating, and diarrhea when taken in large doses—like you might get in an energy bar. What’s more, “reduced sugar” does not necessarily mean reduced calorie—at least, not reduced enough to matter. Malitol, for example, has 75 percent the calories of sugar, and since it’s not as sweet as the real thing, more must be used to achieve the same taste.